An epigenetic mechanism refers to any hereditary influence (in the progeny of cells or individuals) on chromosomal or genetic function that is not accompanied by a change in the DNA sequence (Yoder et al 1997) ; a change in phenotype without a change in genotype. These changes can last through generations of cell divisions. Although it was once thought that there was no new generation of neurons in the nervous system, studies have shown that the brain retains neural stem cells (NSCs) into adulthood and neurogenesis continues to occur. Neural stem cells (NSCs) are the initial cells present in the nervous system and differentiate into the main cell types: oligodendrocytes, astrocytes and neurons. There are three epigenetic mechanisms involved in each of these differentiations; these are DNA methylation, histone modifications, and non-coding ribonucleic acid (ncRNA) expression, leading to activation and silencing of the correct genes at each step. Epigenetic mechanisms have been implicated to play a huge role in several nervous system functions such as neurogenesis, neuronal differentiation and also have roles in higher functions such as memory and cognition. One of the main mechanisms of epigenetics is DNA methylation. DNA methylation occurs in two mechanisms and consists of the addition of a methyl group (-CH₃) via a covalent bond to a side chain of cytosine. DNA methylation is catalyzed by a group of enzymes called DNA methyltransferases (DNMTs). DNMT adds methyl groups to cytosine residues. Cytosines must be immediately followed by a guanine. To be methylated, these are called CpG dinucleotides. About 70% of these dinucleotides are methylated while the rest are found in clusters called CpG islands. There are two types... half of the article......Glass, Non-coding RNAs as Regulators of Gene Expression and Epigenetics, 2011, Oxford Journals, 90 (3), p430-440J. David Sweat. (2009). Experience-dependent epigenetic modifications in the central nervous system. Biol. Psychiatry 65 (3), 191-197.Chwang WB, O'Riordan KJ, Levenson JM, Sweatt JD. ERK/MAPK regulates hippocampal histone phosphorylation following contextual fear conditioning. Learn Mem. 2006;13:322–328Kaili Anier, Anti Kalda, epigenetics in the nervous system. Learn Mem. 2006; 43-72Atd Bio, Epigenetics, 2013, Feng. J. Chang, H. Li E., Fan G. Dynamic expression of the de novo DNA methyltransferases DNMT3a and DNMT3b in the central nervous system. J Neruoscience Res, 2006 (79), p734-746Korzus E, Rosenfeld MG, Mayford M. Histone acetyltransferase CBP activity is a critical component of memory consolidation. Neuron 2004;42:961-72